Klotho- and beclin 1-driven autophagy extends life. We examined the role of beclin 1 in modifying acute kidney injury (AKI) and whether beclin 1 mediates Klotho's known renoprotective action in AKI. AKI was induced by ischemia-reperfusion injury in mice with different levels of autophagy activity by genetic manipulation: wild-type (WT) mice with normal beclin 1 expression and function, mice with normal beclin 1 levels but high activity through knockin of gain-of-function mutant beclin 1 ( ), mice with low beclin 1 levels and activity caused by heterozygous global deletion of beclin 1 ( ), or mice with extremely low beclin 1 activity from knockin of the mutant constitutively active beclin 1 inhibitor Bcl-2 ( ). Klotho was increased by transgenic overexpression ( ) or recombinant Klotho protein administration. After ischemia-reperfusion injury, mice (high autophagy) had milder AKI and and mice (low autophagy) had more severe AKI than WT mice. mice had milder AKI, but its renoprotection was partially attenuated in mice and was significantly reduced, although not completely abolished, in mice. Recombinant Klotho protein conferred more renoprotection from AKI in WT mice than in or mice. Klotho reduced beclin 1/Bcl-2 protein complexes and increased autophagy activity, but this effect was less prominent in mice or cells with . Transfected Bcl2 or Becn1 decreased or increased autophagy activity and rendered cells more susceptible or more resistant to oxidative cytotoxicity, respectively. In conclusion, beclin 1 confers renoprotection by activating autophagy. Klotho protects the kidney partially via disruption of beclin 1/Bcl-2 interactions and enhancement of autophagy activity.